1. Field
The present application relates to thermal management, and more particularly, to micro-scale cooling devices that use electrohydrodynamic (EHD, also known as electro-fluid-dynamic, EFD) technology to generate ions and electrical fields to control the movement of fluids, such as air, as part of a thermal management solution to dissipate heat.
2. Related Art
Devices built using the principle of the ionic movement of a fluid are variously referred to in the literature as ionic wind machines, electric wind machines, corona wind pumps, electro-fluid-dynamics (EFD) devices, electrohydrodynamic (EHD) thrusters and EHD gas pumps. Some aspects of the technology have also been exploited in devices referred to as electrostatic air cleaners or electrostatic precipitators.
In general, electrohydrodynamic (EHD) technology uses ion flow principles to move fluids (e.g., air molecules). Basic principles of EHD fluid flow are reasonably well understood by persons of skill in the art. Accordingly, a brief illustration of ion flow using corona discharge principles in a simple two electrode system sets the stage for the more detailed description that follows.
With reference to the illustration in FIG. 1, corona discharge principles include applying a high intensity electric field between a first electrode 10 (often termed the “corona electrode,” the “corona discharge electrode,” the “emitter electrode” or just the “emitter”) and a second electrode 12. Fluid molecules, such as surrounding air molecules, near the corona discharge region 11 become ionized and form a stream 14 of ions 16 that accelerate toward second electrode 12, colliding with neutral fluid molecules 22. During these collisions, momentum is imparted from the stream 14 of ions 16 to the neutral fluid molecules 22, inducing a corresponding movement of fluid molecules 22 in a desired fluid flow direction, denoted by arrow 13, toward second electrode 12. Second electrode 12 may be variously referred to as the “accelerating”, “attracting”, “collector” or “target” electrode. While stream 14 of ions 16 are attracted to, and neutralized by, second electrode 12, neutral fluid molecules 22 move past second electrode 12 at a certain velocity. The movement of fluid produced by corona discharge principles has been variously referred to as “electric,” “corona” or “ionic” wind and has been defined as the movement of gas induced by the movement of ions from the vicinity of a high voltage discharge electrode 10.
Ozone (O3), while naturally occurring, can also be produced by operation of various electronics devices, including EHD devices, photocopiers, laser printers and electrostatic air cleaners, and by certain kinds of electric motors and generators, etc. However, because ozone can be a respiratory irritant and has, particularly at high concentrations, been associated with certain health issues, ozone emission can be subject to strict regulatory limits such as those set by the Underwriters Laboratories (UL) or the Environmental Protection Agency (EPA). Accordingly, techniques to reduce ozone concentrations have been developed and deployed to catalytically or reactively break down ozone (O3) into the more stable diatomic molecular form (O2) of oxygen.
Improved ozone reduction techniques, and such techniques particularly adapted to EHD devices and deployments are desired.